The present invention relates to a container yoke.
When handling containers or other types of rigid load-carrying receptacles of different standard dimensions there is normally used a yoke or lifting frame which includes a central frame beam and cross-beams which are mounted on the ends of the frame beam, on extension beams, and which are able to move in relation to the frame beam. The free ends of the cross-beams form the four corners of the container yoke or lifting frame and have mounted thereon downwardly depending lifting hooks which can be turned reciprocatingly through ninety degrees, with the aid of a hydraulic system for instance, thereby to engage and disengage corresponding apertures provided at the top of the four corners of the container. Because the cross-beams are able to move, the distance between the cross-beams can be altered to adjust the container yoke to engage features of and, therefore, be able to handle containers of different lengths.
The weight of the yoke, or lifting frame, together with its electric and hydraulic assembly, which functions to maneuver the extension beams and lifting hocks among other things, is quite considerable. The containers handled may be extremely heavy. With this in mind and also bearing in mind that all container yokes, or lifting frames, are handled more or less roughly, it will be understood that great demands are placed on the mechanical strength of all carrying parts, so that these parts will be able to resist the formation of cracks and other forms of fatigue. This demand is met by dimensioning all bars, beams and connections so that, wherever possible, the yoke will be sufficiently strong to withstand all uneven loads to which the container may be subjected. In the case of the earlier known technique, two extension beams together with their respective cross-beams form a welded unit which is moved into an out of the main beams between positions of 20, 40 and 45 feet in length (standard measurements). As a result of the intrinsic weight of the container yoke and the weight of the load handled, a cross-beam or extension beam will often be damaged in some way or another, requiring the beam to be replaced, despite the robust dimensions of the container yoke. Because two extension beams conventionally form a welded unit together with the cross-beams, any repair work is a time-consuming and expensive operation. Furthermore, the welded unit is difficult to manufacture, since it is imperative that the longitudinally extending extension beams be parallel with one another. This parallelism can be jeopardized by impact on one corner of the yoke, therewith rendering the yoke unserviceable.